ISO 6974-5:2014
Natural gas - Determination of composition and associated uncertainty by gas chromatography - Part 5: Isothermal method for nitrogen, carbon dioxide, C1 to C5 hydrocarbons and C6+ hydrocarbons

Standard No.

ISO 6974-5:2014

Release Date

2014

Published By

International Organization for Standardization (ISO)

Latest

ISO 6974-5:2014

Scope

This part of this International Standard describes a gas chromatographic method for the quantitative determination of the content of nitrogen, carbon dioxide and C1 to C5 hydrocarbons individually and a composite C6+ measurement, which represents all hydrocarbons of carbon number 6 and above in natural gas samples. It is applicable to the analysis of gases containing constituents within the working ranges given in Table 1. Table 1 — Component working ranges Mole fraction Component Nitrogen N2 Min. 0,1 % Max. 22 Carbon dioxide CO2 Propane C3H80,05 neo-Pentane neo-C5H120,0050,35 C6 + 0,0050,35 Methane Ethane iso-Butane n-Butane iso-Pentane n-Pentane Hexanes + CH4 C2H6 i-C4H10 n-C4H10 i-C5H12 n-C5H120,0515341000,012,00,10,010,0050,00523102,00,350,35 NOTE 1 The working ranges in Table 1 are those for which the method has been shown to be satisfactory, and are offered for guidance. However, there is no reason why wider ranges should not be used, provided that the successful measurement of such wider ranges has been demonstrated. NOTE 2 Hydrocarbons above n-pentane are expressed as the “pseudo-component” C6+ which is measured as one composite peak and calibrated as such. The properties of C6+ are calculated from an extended analysis of the individual C6 and higher hydrocarbons. NOTE 3 Oxygen is not a normal constituent of natural gas and would not be expected to be present in gas sampled to an online instrument. If any oxygen is present as a result of air contamination, it will be measured with the nitrogen. The resulting measured (nitrogen + oxygen) value will be in error to a small extent because of the slight difference between the detector responses of oxygen and nitrogen. NOTE 4 The helium and argon contents are assumed to be sufficiently small and unvarying that they need not be analysed for. NOTE 5 The gas sample shall not contain any hydrocarbon condensate and/or water. 1

ISO 6974-5:2014 Referenced Document

• ISO 10723:2012 Natural gas - Performance evaluation for analytical systems
• ISO 6974-1:2012 Natural gas - Determination of composition and associated uncertainty by gas chromatography - Part 1: General guidelines and calculation of composition
• ISO 6974-2:2012 Natural gas - Determination of composition and associated uncertainty by gas chromatography - Part 2: Uncertainty calculations
• ISO 6976:1995 Natural gas - Calculation of calorific values, density, relative density and Wobbe index from composition
• ISO 7504:2001 Gas analysis - Vocabulary
• ISO/IEC Guide 98-3:2008 Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in measurement (GUM:1995)

ISO 6974-5:2014 history

• 2014 ISO 6974-5:2014 Natural gas - Determination of composition and associated uncertainty by gas chromatography - Part 5: Isothermal method for nitrogen, carbon dioxide, C1 to C5 hydrocarbons and C6+ hydrocarbons
• 2000 ISO 6974-5:2000 Natural gas - Determination of composition with defined uncertainty by gas chromatography - Part 5: Determination of nitrogen, carbon dioxide and C<(Index)1> to C<(Index)5> and C<(Index)6+> hydrocarbons for a laboratory and on-line process application usi